The present invention relates to a modular high-frequency converter. The invention further relates to a method for operating such a converter.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Conventional modular high-frequency converters (abbreviated to MHF converter) are designed to convert a DC voltage from a traction battery of the vehicle into a number of AC voltages. The individual AC voltages in such cases are generated by a number of submodules which are connected in series into the supply circuit of the traction battery. Each submodule is connected here on the input side to the supply circuit via a half bridge. To generate the AC voltage each submodule has a single-phase full bridge (H bridge) on its output side, which is connected via a load circuit to a phase winding of the drive motor of the vehicle. Within the submodule the input-side half bridge and the full bridge are connected in parallel, together with a link circuit capacitance, in a (DC) link circuit.
In normal operation (drive mode) of the MHF converter, in which electrical power is transported via the submodules of the converter out of the supply circuit into the respective load circuit, the input-side half bridges of the submodules are operated in collaboration with an inductance arranged in the supply circuit as boost converters. For this purpose the DC link circuit capacitances of the submodules are usually switched into the supply circuit with offset clocking. For this purpose, the input-side half bridges are activated as a rule with periodic carrier signals which are offset by the same phase angle.
In addition to the drive mode, the input-side half bridges of the submodules can also be operated in a feedback mode, in which electrical power is fed back from the load circuit via the respective associated submodule into the supply circuit.
The DC link circuit voltages of the submodules are regulated individually for each submodule by variation of the sampling cycle (also known as the control factor, pulse-pause ratio or duty cycle), with which the respective input-side half bridge of the respective submodule is activated.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved MHF converter and an improved method for its operation.